1. Field of the Invention
The present invention relates to a method and apparatus for estimating error in a multi-axis controlled machine, and more particularly, applicable to any type of machine configurations in order to estimate and verify in advance the final position and posture of the machine affected by perplexedly interlinked geometric errors.
2. Description of Related Art
Multi-axis controlled machines are a type of mechanical apparatus that includes two or more drive axes. A multi-axis controlled machine can be a multi-axis machine tool that has a combination of a number of linear or rotary drive axes, such as a linear slide or a rotary or tilting table, a multi-axis articulated robot, a Coordinate Measuring Machine (CMM), or the like. FIG. 1 shows a five-axis machine tool as an example of a multi-axis controlled machine.
The multi-axis controlled machines have many geometrical errors, such as error of each drive axis and error between drive axes, which are perplexedly interlinked to each other, thereby resulting in the deviation of final posture (i.e., position and orientation) when the multi-axis controlled machine is driven. Various error synthesis models, as mathematical expressions, are derived depending on the structures and shapes of the multi-axis machines.
Meanwhile, in the stage of designing or fabricating multi-axis controlled machines, it is necessary to measure and evaluate geometric errors of the machines in order to verify the performance and compensate for the errors of the machines. Devices used to measure such errors generally include a laser interferometer, a ball bar, a capacitance sensor, an autocollimator, a Position-Sensitive Detector (PSD), and the like. In particular, a variety of measuring methods has been studied and developed for multi-axis controlled machines having rotary axes due to the difficulty involved in measurement.
In addition, in order to estimate the performance of the multi-axis controlled machines, it is necessary to evaluate the final error effects of a number of geometric errors. However, in the multi-axis controlled machines having different configurations, technologies that define the relationships between a number of geometric errors, such as the error of a drive axis and the error between drive axes, and derive final error effects have not been automated yet. Thus, complicated and difficult mathematical calculation has to be performed every time, according to the configuration of a multi-axis controlled machine. In addition, it becomes very difficult for engineers to directly evaluate the contribution of respective errors to the final posture error. In particular, the greater the number of drive axes, the more significant these problems are.
Therefore, conventional error estimation technologies, which are used in general industrial sites, can only measure and estimate a small number of errors of a single axis or a small number of axes using an error estimation device, or estimate the performance of processing the errors by measuring the final result obtained by directly processing the errors. In addition, the accuracy of estimation is low.
The information disclosed in this Background of the Invention section is only for the enhancement of understanding of the background of the invention and should not be taken as an acknowledgment or any form of suggestion that this information forms a prior art that would already be known to a person skilled in the art.